Victoria’s water minister said the actions of Labor and the Greens in the Senate had killed the Murray-Darling basin plan.Photograph: Photography by Mangiwau/Getty Images

The New South Wales government said its plan to walk away from the Murray-Darling basin plan will free it from “the whim of politicking”, while blaming Labor and the Greens for bringing the vital water-sharing agreement to the “brink of collapse”.

NSW regional water minister, Niall Blair, said the state government would act “calmly” in its next steps, and honour any existing commitments made under the Murray-Darling basin plan.

“Walking away from the plan allows us to focus on achieving all the environmental, social and economic outcomes the plan was designed to achieve, without being at the whim of politicking from federal Labor, the Greens and the South Australians fighting for votes,” Blair said in a statement to Guardian Australia.

“Our stance is about securing the future of western NSW – the Labor party seems more concerned about its electoral prospects in South Australia. It is federal Labor and the Greens in the Senate who have brought the Murray Darling basin plan to the brink of collapse.”

Labor and the Greens blocked changes in the Senate on Wednesday that would have cut the amount of water returned to the environment in northern NSW and Queensland. The changes would have reduced water returned by 70GL.

Their actions also angered Victoria. On Thursday morning, the state’s water minister, Lisa Neville, said the Murray-Darling basin plan was now “over”. “We said if these motions get disallowed the plan is over. It’s not walking away, the plan is over,” Neville told ABC radio.

But the Victorian premier, Daniel Andrews, later pledged to continue negotiations with the federal government.

Andrews said it appeared it would be “difficult” to find a way to work with the commonwealth government.

“It’s now for us to work with the commonwealth government to find a way forward and that does appear difficult,” Andrews said. “What happened in the Senate last night was a very disappointing outcome for communities, for irrigators and indeed for the environment.”

The Murray-Darling basin plan is the product of decades of reform aimed at preserving the health of Australia’s largest inland river system and governing water use by irrigators, industry and state governments in four jurisdictions.

Queensland on Thursday pleaded with NSW and Victoria not to walk away.

Queensland’s natural resources minister, Anthony Lynham, urged his southern counterparts to stay in the plan, saying he’d been reassured by the federal shadow environment and water minister, Tony Burke, that there was a way forward.

“I have been working behind the scenes with both sides of politics, I have been on the phone incessantly,” he said on Thursday.

“I haven’t been fighting this out in the media like some of my southern colleagues, I’ve just been working my way through.

“I would urge NSW and Victoria to stay in the plan. It’s been so many years, we need to end the uncertainty.”

His NSW counterpart, Blair, said it was up to the federal government to intervene and fix the “Senate’s mess”.

“This agreement took 100 years to make, so we will approach the next steps calmly and in the best interests of the environment and our regional communities in NSW,” Blair said.

“Canberra has options to fix the Senate’s mess, and I would encourage the federal government to keep working with Tony Burke to come to a position.”

Federal Labor has indicated it is still willing to continue negotiations, and opposition leader Bill Shorten was hopeful a deal could be reached.

“I think there’s a deal to be done. I think that people of goodwill can make it work,” Shorten said on Thursday. “But the government really has left it at five minutes to midnight ... They’re so consumed about their own soap opera that the big issues, the issues which affect jobs and agriculturalists and affect climate - that’s just not getting the attention it deserves.”

Environmentalists and NSW Labor have warned walking away from the agreement would be legacy-defining for the NSW government and spell disaster for the environment.

The Australian Conservation Foundation campaigns director, Paul Sinclair, said NSW “seems obsessed” with destroying “decades of river reform that was sparked by Prime Minister John Howard”.

“It is now incumbent on NSW Premier Gladys Berejiklian to pull the NSW Nationals into line and get the basin plan back on track,” Sinclair said.

Sinclair accused the NSW government of bowing to powerful irrigators. “You would think the NSW Government would have a little more shame given the serious allegations of rorting and mismanagement of the river on its watch,” Sinclair said on Thursday.

The reduction, though, is strongly opposed by farmers downstream of Bourke. Environmentalists and scientists have warned it puts the river’s health at risk, and that the cut to environmental recovery targets in the upper Darling would undermine the plan.

The NSW shadow water minister, Chris Minns, said if NSW pulled out, it would place the NSW Nationals in charge of “writing the rules and ensuring compliance for water management on the Darling”.

“Talk about putting Dracula in charge of the blood bank,” Minns said. “If the last seven years have taught us anything it is that you cannot trust the NSW Nationals, they will always put their mates first.

“The NSW Nationals through their scandalous management of the water portfolio have brought the Murray-Darling River network to the brink of collapse.”